Synthetic WSe2 monolayers with high photoluminescence quantum yield

Hyungjin Kim; Geun Ho Ahn; Joy Cho; Matin Amani; James P Mastandrea; Catherine K Groschner; Der-Hsien Lien; Yingbo Zhao; Joel W Ager 3rd; Mary C Scott; Daryl C Chrzan; Ali Javey

doi:10.1126/sciadv.aau4728

Synthetic WSe₂ monolayers with high photoluminescence quantum yield

Sci Adv. 2019 Jan 4;5(1):eaau4728. doi: 10.1126/sciadv.aau4728. eCollection 2019 Jan.

Authors

Hyungjin Kim^{1

2}, Geun Ho Ahn^{1

2}, Joy Cho^{1

2}, Matin Amani^{1

2}, James P Mastandrea^{2

3}, Catherine K Groschner^{2

3

4}, Der-Hsien Lien^{1

2}, Yingbo Zhao^{1

2}, Joel W Ager 3rd^{2

3}, Mary C Scott^{2

3

4}, Daryl C Chrzan^{2

3}, Ali Javey^{1

2}

Affiliations

¹ Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, CA 94720, USA.
² Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
³ Department of Materials Science and Engineering, University of California at Berkeley, Berkeley, CA 94720, USA.
⁴ National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.

Abstract

In recent years, there have been tremendous advancements in the growth of monolayer transition metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD). However, obtaining high photoluminescence quantum yield (PL QY), which is the key figure of merit for optoelectronics, is still challenging in the grown monolayers. Specifically, the as-grown monolayers often exhibit lower PL QY than their mechanically exfoliated counterparts. In this work, we demonstrate synthetic tungsten diselenide (WSe₂) monolayers with PL QY exceeding that of exfoliated crystals by over an order of magnitude. PL QY of ~60% is obtained in monolayer films grown by CVD, which is the highest reported value to date for WSe₂ prepared by any technique. The high optoelectronic quality is enabled by the combination of optimizing growth conditions via tuning the halide promoter ratio, and introducing a simple substrate decoupling method via solvent evaporation, which also mechanically relaxes the grown films. The achievement of scalable WSe₂ with high PL QY could potentially enable the emergence of technologically relevant devices at the atomically thin limit.